The present invention relates to a method and a device for determining the optimum procedure for a job change on a printing-material processing machine with at least one control computer.
Unlike web-fed rotary printing presses used in newspaper applications, in the case of sheet-fed offset printing presses, print jobs are changed relatively frequently. In this case, it is necessary to replace the printing plates on the plate cylinders and often also to change the printing inks. This involves a number of further operations, including, for example, washing of cylinders in the printing press. Some of these operations during a job change take place concurrently; others have to be carried out consecutively so that the manner in which the operations during the job change are organized is of considerable importance.
In conventional printing presses, the order of operations during a job change is fixed so that the operating personnel have no possibility to change this order, but have to follow the procedure determined by the printing press. However, fixed procedures during the job change inevitably lead to approximately identical set-up and downtimes when changing between two print jobs, independently of which operations are actually required for the particular job change. German Patent No. DE 196 31 469 C1, related to U.S. Pat. No. 5,930,468 which is hereby incorporated by reference herein, describes a method which is intended to optimize and minimize the set-up and downtimes for several changes between several consecutive print jobs. To this end, the method uses a data processing system that controls a printing press so as to bring the pending print jobs into such an order that the set-up and downtimes during the print job changes to be carried out will be as short as possible. To this end, the image contents of different print jobs are compared image element by image element as well as their respective color separations, making it possible to predict the operations for making printing forms and to establish the order of print jobs on the basis of the totality of operations. Thus, it is known from German Patent No. DE 196 31 469 to calculate the order of print jobs in a manner allowing the print jobs, including print jobs changes, to be carried out in as short an overall time as possible. However, the procedure known from the prior art mentioned in the previous section is only successful if a certain number of print jobs is known in advance so that they can be brought into a specific optimum order. According to the prior art, however, a single change between two print jobs cannot be optimized.